An electrical submersible pump (“ESP”) assembly for wells typically comprises a submersible motor that drives a pump, typically a centrifugal pump. The pump assembly is usually suspended on a string of tubing within the well. The power cable to the motor is strapped alongside the tubing. Periodically, the pump assembly has to be retrieved for maintenance or repair, and this step requires pulling the tubing. Pulling the tubing requires a workover rig and is time consuming, particularly for offshore installations.
In some cases a dual tandem pump assembly is used to provide more lift. Normally two pumps are connected together and driven by a single motor. The pumps thus operate in unison with each other. Repair or replacement of either pump requires pulling the tubing and the entire assembly.
Often a pressure and temperature sensor will be mounted to the base of the motor for sensing the pressure and temperature of the dielectric liquid within the motor. The power to the motor fluid sensor and the signals are superimposed on the ESP power cable. Another measuring tool comprises a reservoir sensor, which is an electrical device that senses various characteristics of the producing reservoir of the well on the exterior of the motor. These tools typically send signals up a dedicated communication line extending to the surface.